package com.week1.day01;

import java.util.Scanner;
public class Demo01 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("输入三角形的底");
        int di = sc.nextInt();
        int gao = sc.nextInt();
        System.out.println(di*gao/2);
    }
}
